This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
HDR (High Dynamic Range) videos generally represent a greater range of luminance levels than that can be achieved by conventional SDR (Standard Dynamic Range) videos, which usually have a 8- or 10-bit dynamic range. To compress or represent HDR videos, as shown in FIG. 1, some existing methods first perform forward conversion (110), which may include a conversion from HDR linear signals to non-linear signals, color space conversion, bit-depth reduction/quantization, and chroma down-conversion. The signals after forward conversion can then be compressed using a video encoder (120), for example, an HEVC (High Efficiency Video Encoding) encoder that supports 8-bit and 10-bit video formats. At the decoder side, the bitstream is decoded using a video decoder (130), for example, an HEVC decoder, and then is converted to HDR video signals using backward conversion (140), which may include color space conversion, bit-depth inverse quantization, chroma up-conversion, and conversion from non-linear signals to HDR linear signals.
SMPTE 2084 defines a transfer function that takes into account the sensitivity of the HVS (Human Visual System) to luminance, which applies an OETF (Opto-Electronic Transfer Function) curve to each pixel independently. The forward conversion module (110) may use the OETF curve and bit-depth quantization to transform the HDR videos to video signals represented with fewer bits, for example, to 10 or 12-bit signals according to SMPTE 2084, and the backward conversion module (140) may use an inverse OETF curve that corresponds to the OETF curve, for example, the Perceptual Quantizer (PQ) EOTF curve.